1. Field of the Invention
The invention concerns isolating switches comprising a plurality of electrical switches and in particular isolating switches with five switches used as phase inverters in a three-phase system, for example for pumping sets in which the alternator can be operated as a motor to reverse the rotation direction of the rotating machine.
2. Description of the Prior Art
FIG. 1 is a highly schematic representation of a phase inverter isolating switch of the above kind including five switches C1 through C5. It is connected between three phase inputs A, B, C and three phase outputs A', B', C'. Each switch has a fixed first contact 1 and a second contact 2 that cooperates with the first contact. The second contact 2 moves between a first position in which is it electrically connected to the fixed contact (switches C2, C3, C4) and a second position in which it is separated from the fixed contact (switches C1 and C5).
As can be seen in FIG. 1, the mobile contacts 2 of the switches C1 and C4 are electrically connected to the phase input C, the mobile contacts 2 of the switches C2 and C5 are electrically connected to the phase input A and the mobile contact 2 of the switch C3 in connected to the phase input B. The fixed contacts 1 of the switches C1 and C2 are electrically connected to the phase output A', the fixed contacts 1 of the switches C4 and C5 are electrically connected to the phase output C' and the fixed contact 1 of the switch C3 is electrically connected to the phase output B'.
FIG. 2 is a table summarizing the operation of this isolating switch used as a phase inverter. In a first position E1 of the isolating switch the switches C1 and C5 are open (in the position indicated O) and the switches C2 through C4 are closed (in the position indicated F). In this position the phase input A is electrically connected to the phase output A', the phase input B is electrically connected to the phase output B' and the phase input C is electrically connected to the phase output C'. In a second position E0 of the isolating switch the switches C1 through C5 are all open. In this position the inputs of the isolating switch are all separated from its outputs. In a final third position E2 of the isolating switch the switches C1, C3 and C5 are closed and the switches C2 and C4 are open. In this position the phase input C is electrically connected to the phase output A', the phase input B is electrically connected to the phase output B' and the phase input A is electrically connected to the phase output C'. The result of this is that the phases A and C at the output of the isolating switch are reversed relative to the E1 position of the isolating switch.
The isolating switch is designed so that it necessarily goes from the position E1 to the position E2 (or vice versa) via the position E0, other possible connections between the inputs and outputs of the isolating switch being prohibited.
The aim of the invention is to propose a switch arrangement for an isolating switch of the above kind for use as a phase inverter in which the switches are actuated by a single actuator whilst avoiding the prohibited connection possibilities.